Multiple sclerosis (MS) is a progressive neurologic disorder that is likely to have an autoimmune basis. We have been testing the safety and efficacy of cladribine (2-CdA) as a treatment for MS. Other current treatments are unsatisfactory, with Beta Interferon and Copaxone having a partial effect on relapses in MS. We have completed treatment trials in chronic progressive MS and have shown that cladribine, an immunosuppressive agent, retards the progression of the disease for two years or longer. A double-blind, placebo-controlled clinical trial of cladribine in relapsing-remitting MS (subproject #288) has just been completed.